Fix gdb.arch/amd64-tailcall-*.exp with -fPIE/-pie

  Hi,

When running gdb.arch/amd64-tailcall-*.exp with target board
unix/-fPIE/-pie, we get:
...
FAIL: gdb.arch/amd64-tailcall-cxx.exp: bt
FAIL: gdb.arch/amd64-tailcall-noret.exp: bt
FAIL: gdb.arch/amd64-tailcall-self.exp: bt
...

The first FAIL in more detail, compared to a nopie run:
...
(gdb) bt
 #0  b ()
-#1  0x00000000004004df in a (q=<optimized out>)
+#1  0x0000000000000672 in ?? ()
-#2  0x00000000004003d5 in main (argc=<optimized out>, argv=<optimized out>)
+#2  0x0000555555554535 in main (argc=<optimized out>, argv=<optimized out>)
-(gdb) PASS: gdb.arch/amd64-tailcall-self.exp: bt
+(gdb) FAIL: gdb.arch/amd64-tailcall-self.exp: bt
...
shows an unrelocated address for function a.

The problem is that pretend_pc uses the pc field from a struct call_site
without adding the missing relocation offset.

Fix this by adding the appropriate offset.

Tested on x86_64-linux, with and without -fPIE/-pie.

OK for trunk?

Thanks,
- Tom

[gdb] Fix gdb.arch/amd64-tailcall-*.exp with -fPIE/-pie

gdb/ChangeLog:

2019-08-09  Tom de Vries  <tdevries@suse.de>

	* dwarf2-frame-tailcall.c (pretend_pc): Add relocation offset to pc
	field of struct call_site.

---
 gdb/dwarf2-frame-tailcall.c | 30 ++++++++++++++++++++++++++++--
 1 file changed, 28 insertions(+), 2 deletions(-)
  

On 8/9/19 11:48 AM, Tom de Vries wrote:
> @@ -240,14 +242,38 @@ pretend_pc (struct frame_info *this_frame, struct tailcall_cache *cache)
>    gdb_assert (next_levels >= 0);
>  
>    if (next_levels < chain->callees)
> -    return chain->call_site[chain->length - next_levels - 1]->pc;
> +    {
> +      struct call_site *call_site
> +	= chain->call_site[chain->length - next_levels - 1];
> +      CORE_ADDR addr = call_site->pc;
> +      struct dwarf2_per_objfile *dwarf2_per_objfile
> +	= call_site->per_cu->dwarf2_per_objfile;
> +       struct objfile *objfile = dwarf2_per_objfile->objfile;
> +       CORE_ADDR baseaddr
> +	 = ANOFFSET (objfile->section_offsets, SECT_OFF_TEXT (objfile));
> +       struct gdbarch *gdbarch = get_objfile_arch (objfile);
> +       addr = gdbarch_adjust_dwarf2_addr (gdbarch, addr + baseaddr);
> +      return addr;
> +    }
>    next_levels -= chain->callees;
>  
>    /* Otherwise CHAIN->CALLEES are already covered by CHAIN->CALLERS.  */
>    if (chain->callees != chain->length)
>      {
>        if (next_levels < chain->callers)
> -	return chain->call_site[chain->callers - next_levels - 1]->pc;
> +	{
> +	  struct call_site *call_site
> +	    = chain->call_site[chain->callers - next_levels - 1];
> +	  CORE_ADDR addr = call_site->pc;
> +	  struct dwarf2_per_objfile *dwarf2_per_objfile
> +	    = call_site->per_cu->dwarf2_per_objfile;
> +	  struct objfile *objfile = dwarf2_per_objfile->objfile;
> +	  CORE_ADDR baseaddr
> +	    = ANOFFSET (objfile->section_offsets, SECT_OFF_TEXT (objfile));
> +	  struct gdbarch *gdbarch = get_objfile_arch (objfile);
> +	  addr = gdbarch_adjust_dwarf2_addr (gdbarch, addr + baseaddr);
> +	  return addr;
> +	}

It seems like there's a repeated pattern here.  How about
factoring out the common code to a function?

Thanks,
Pedro Alves